Bifunctional CePO 4 /CeO 2 nanocomposite as a promising heterogeneous catalyst for the enhancement of the ozonation recovery effect in the presence of chloride ions

The degradation of organics through ozonation is strongly reduced by chloride ions. Although the efficiency of such processes can be recovered in the presence of homogeneous phosphates, the addition of these chemicals to water is problematic because of the generation of secondary wastes. Phosphates are known as one of the most important biogens responsible for the eutrophication of rivers and lakes. Thus, their worldwide application should be limited. The main goal of this work was to characterize the performance of solid-state cerium(III) phosphate (CePO 4 ), cerium dioxide (CeO 2 ), and bifunctional CePO 4 /CeO 2 nanocomposite as substitutes for homogeneous phosphates during the ozonation of benzoic acid (BA) in the presence of chlorides. All solid-state samples used in this study were synthesized by facile hydrothermal method and thoroughly characterized. It was documented that heterogeneous CePO 4 showed significantly better ozonation recovery effect than homogeneous phosphates. It was also established that the process efficiency could be further enhanced by using the bifunctional nanocomposite. Tests with the use of tert -butanol as a hydroxyl radical scavenger revealed that the improved ozonation efficiency in the presence of CePO 4 /CeO 2 resulted from the action of HO • radicals which were the key reactive oxygen species responsible for the recovery of BA degradation in the presence of chlorides.